1. Field of the Invention
This invention relates generally to containers, and particularly to containers of the type having an easy-open end that is designed to be opened by a pull-tab mechanism.
2. Description of the Related Technology
The term “easy open end” is used generally for that class of ends for containers that are provided with a built-in mechanism for permitting the consumer to open the container at the end for access to the ingredients within the container, without requiring the use of a can opener or other external tool. One conventional easy open end employs a pull tab having a pointed nose, the pull tab being riveted to the panel of the end so that the nose rests adjacent a weakened area along the periphery of the end panel. To open, the pull tab is rotated about the rivet, causing the nose to fracture the weakened area. Further pulling of the tab away from the end panel then causes the remainder of the weakened peripheral to rupture, thereby permitting the entire end to be opened.
One type of easy-open end that is in wide use is the so called “full-open” end, in which a peripheral score, generally circular in configuration, is formed in the end panel at or adjacent to the periphery thereof to permit its complete removal. Full-open type cans are to be distinguished from those self opening cans which have a comparatively small removable section which, when opened, provide a comparatively small hole for dispensing the product. The latter type of can end is more appropriate for packaging soda, beer, or other liquids. Full-open type cans, on the other hand, are suitable for packaging solid products such as candy, nuts, meats, or ground coffee.
One generally recognized disadvantage of easy-open ends relates to the sharp edges that result after the can end is opened and the consequential safety issues. U.S. Pat. No. 4,511,299 to Zysset addresses these issues and introduced the concept of using blunt, protective shoulders formed by folding the panel end wall near the score line. The forming method that was described in the Zysset patent, which was never successfully placed into production, is depicted in FIGS. 1 through 6. As may be seen in FIG. 1, the starting material is a planar can end blank 10. The end blank 10 is first subjected to a first forming operation to form bend 16 and a portion of a side curl 18 at the peripheral edge of the end 10. As shown in FIG. 2, the end is then subjected to a second operation bending and forming step to create a pair of concentric grooves 20, 22 which define inner and outer beads 21, 23 that extend below the second, inner surface 14 of the end 10. Also formed is a central bead 24, which extends above the level of the first, outer surface 12 of the end 10.
Referring now to FIG. 3, the end 10 was described to be subjected to another forming step wherein the portion of the end 10 inside the bead 21 is rolled upward, and the second bead 23 is extended downwardly. Thereafter, as is shown in FIG. 4, a score 28 is formed on the central bead 24, and then the inner and outer beads 21, 23 are forced toward the inside surface 14 and the central bead 24 is forced toward the outside surface 12 until the inner and outer beads 21, 23 abut the central bead 24 to provide blunt, protective shoulders underneath the score line 28 (see FIG. 5). The protective shoulders formed by the inner and outer beads 21, 23 of this double-fold configuration lie in a common plane which is substantially parallel to, but spaced from the plane of the end 10. As is shown in FIG. 6, the completed end is provided with a pull-tab 34, the extremity of which extends adjacent to the score line 28 to permit the end to be opened in a conventional manner. As may be seen in FIGS. 6 and 7, a completed end fabricated in accordance with the method shown in FIGS. 1-5 includes the central bead 24 that contains the score line which is flush with the end 10 and resides essentially in the plane of the end 10, and concentric recesses 30, 32 that surround the central bead. The recesses 30, 32 are formed by the specific bending technique described below with respect to the inner and outer beads 21, 23.
While the cut protection provided by double-fold configurations such as those disclosed in the Zysset patent is substantial, the sharp edge of an end panel that has been separated along a score line can still present a threat of finger cuts to a consumer who might unfortunately contact the edge from an unfavorable direction or orientation wherein the blunt protective shoulders of the double-fold beads fail to prevent substantial contact between the edge and the consumer's finger.
A need exists for an improved easy-open end and a process for making such an end that improves the quality of cut protection that is afforded to a consumer.